Safety in the use of small volumes of hypertonic saline solution for hypovolaemic shock and in the treatment of intracranial hypertension has been demonstrated in studies in the field of resuscitation. There is little experience of this for septic shock in humans. Beneficial immunomodulatory effects have been detected in pre-clinical studies. Interactions with the pituitary-adrenal axis and with the secretion of anti-diuretic hormone are varied and suggestive, but are not sufficiently understood. On the other hand, vasopressin has cardiovascular, osmoregulatory, and coagulation effects, and also acts on the hypothalamic-pituitary-adrenal axis. There is a relative deficit of vasopressin in septic shock. Its use in these patients does seem to have any advantages as regards mortality, but may be beneficial in patients at risk from acute renal failure, or those who receive corticosteroids. Terlipressin is a vasopressin analogue that has also been studied. The synergy between vasopressin and hypertonic saline is a hypothesis that is mainly supported in pre-clinical studies. The use of hypertonic saline solution in septic shock, although promising, is still experimental, and must be restricted to the field of controlled clinical trials.